Early aseptic loosening of the tibial component at the cement-implant interface in total knee arthroplasty: a narrative overview of potentially associated factors

Adhesion of bone cement to porous and nonporous 3D printed surfaces

Bone cement is an adhesive commonly used to bond orthopedic implants to bone during a surgical procedure. Total joint replacements such as total knee, hip, shoulder, or ankle arthroplasties have metal or polymer components that are commonly cemented. However, implant failures can occur via debonding at the implant-cement interface, suggesting sub-optimal adhesion of the cement to the implant. In parallel, the orthopedic implant industry is seeing a significant rise in additive manufacturing (AM), which enables the seamless integration of surface porosity enhanced osseointegration in cementless procedures. However, there is a lack of foundational data or understanding of how bone cement adheres to 3D printed surfaces as a function of varying topography. This study evaluates adhesion of cement to clinically relevant printed implant surfaces, porous topographies, and materials. Adhesion strength of cemented samples was tested in shear. Surface porous layers were compared to traditional implant surface finishes (blasted, machined, polished). The impact of 3D printed surface porosity size and depth was also investigated. Testing revealed that the adhesive strength of porous surfaces (26.3 ± 3.1 MPa) was more than double the adhesive strength of all non-porous surfaces (the highest being the as-printed surface with a strength of 11.3 ± 2.5 MPa). The study also demonstrated porosity and layer-depth dependent performance trade-offs, with the best performing group having a 2x2x2 mm3 unit cell size and 0.50 mm layer depth and a shear strength of 26.31 ± 3.10 MPa. These results provide a foundation for improving designs of emerging 3D printed orthopedic implants that can be both cemented and cementless.

Aseptic Tibial Loosening Is Associated With Thickness of the Cement: A Radiographic Case-Control Study

BACKGROUND

The cementation technique is crucial for achieving adequate fixation and optimal survivorship in total knee arthroplasty (TKA). The thickness of the cement at the tibial bone-implant surface may be related to aseptic tibial loosening. However, to date, no studies have demonstrated a direct association between cement thickness and rates of aseptic tibial loosening.

METHODS

We performed a retrospective review to identify 28,327 primary cemented TKAs with at least 2 years of follow-up at an academic health system from 2013 to 2021. A total of 115 cases underwent revision surgery for aseptic tibial loosening. Cases where the implant was recalled specifically for loosening (n = 23) were excluded. The remaining 92 aseptic tibial loosening cases were 2:1 propensity score matched and implant matched to control patients who did not have tibial loosening. There were two independent reviewers who then measured the thickness of the cement interface in 10 locations along the bone-implant interface from initial postoperative radiographs. The averages of the reviewers' measurements were calculated and then compared using independent t-tests.

RESULTS

Aseptic tibial loosening cases involving implant A tibial baseplate (n = 75) had significantly thinner cement interfaces than matched controls at all the 10 locations measured. Aseptic loosening cases involving implant B (n = 17) also displayed a thinner cement interface than matched controls in all locations, but this result was only statistically significant at the medial baseplate, medial keel, lateral keel, anterior keel, and posterior baseplate.

CONCLUSIONS

In two widely used TKA systems, tibial aseptic loosening was associated with significantly thinner cement interfaces when compared to propensity-matched controls in two different implant types. Further prospective studies are needed to identify the optimal keel preparation and design as well as minimal cement interface thickness to avoid implant loosening.

LEVEL OF EVIDENCE

III.

Double-Butter: A Cementation Technique That Significantly Reduces Lipid Contamination of the Tibial Baseplate in Total Knee Arthroplasty

Background

Aseptic loosening is the most common aseptic failure modality following total knee arthroplasty. Recent literature suggests that the implant-cement interface is the "weak-link" in fixation and lipid contamination may drive this debonding pattern. Therefore, the purpose of this study was to determine if the "double-butter" technique would significantly decrease lipid contamination of the tibial tray.

Methods

Transparent acrylic models of 7 different tibial baseplates were created to allow for direct visualization of fluid contamination of the implant-cement interface during experimental cementation. Three cementation techniques were then employed in triplicate for each implant: coating only the tibia ("single butter") and coating of the tibia and baseplate (with and without keel included; "double-butter"). A dye was added centrally to simulate lipid contamination. After each trial, the degree of implant-cement contamination was calculated. Standard statistical analyses were conducted.

Results

With the double-butter technique, there was a significant reduction in contamination for all studied implant designs (range: 0%-7%; P < .05) and contamination was eliminated when the entire implant was coated prior to implantation. The single-butter technique resulted in contamination of 16%-43% of the tibial undersurface. There were significant differences in percent contamination between component designs (P < .05).

Conclusions

Cementation technique and implant design each influenced baseplate lipid contamination. While significant differences were noted between keel geometries, we found that the double-butter technique effectively eliminated baseplate contamination, even in the most susceptible designs in this study. We therefore advocate for the incorporation of the double-butter technique to limit lipid contamination and potentially reduce aseptic tibial loosening.

Radiolucent lines and revision risk in total knee arthroplasty using the conventional versus the Attune S+ tibial baseplate

Aims

This multicentre retrospective observational study's aims were to investigate whether there are differences in the occurrence of radiolucent lines (RLLs) following total knee arthroplasty (TKA) between the conventional Attune baseplate and its successor, the novel Attune S+, independent from other potentially influencing factors; and whether tibial baseplate design and presence of RLLs are associated with differing risk of revision.

Methods

A total of 780 patients (39% male; median age 70.7 years (IQR 62.0 to 77.2)) underwent cemented TKA using the Attune Knee System) at five centres, and with the latest radiograph available for the evaluation of RLL at between six and 36 months from surgery. Univariate and multivariate logistic regression models were performed to assess associations between patient and implant-associated factors on the presence of tibial and femoral RLLs. Differences in revision risk depending on RLLs and tibial baseplate design were investigated with the log-rank test.

Results

The conventional and novel Attune baseplates were used in 349 (45%) and 431 (55%) patients, respectively. At a median follow-up of 14 months (IQR 11 to 25), RLLs were present in 29% (n = 228/777) and 15% (n = 116/776) of the tibial and femoral components, respectively, and were more common in the conventional compared to the novel baseplate. The novel baseplate was independently associated with a lower incidence of tibial and femoral RLLs (both regardless of age, sex, BMI, and time to radiograph). One- and three-year revision risk was 1% (95% CI 0.4% to 1.9%)and 6% (95% CI 2.6% to 13.2%), respectively. There was no difference between baseplate design and the presence of RLLs on the the risk of revision at short-term follow-up.

Conclusion

The overall incidence of RLLs, as well as the incidence of tibial and femoral RLLs, was lower with the novel compared to the conventional tibial Attune baseplate design, but higher than in the predecessor design and other commonly used TKA systems.

Diagnostic performance of SPECT/CT for identification of aseptic loosening after total knee and hip arthroplasty: a systematic review and meta-analysis

Despite an increasing number of studies examining the effect of Single-Photon Emission Computed Tomography/ Computed Tomography (SPECT/CT) on improvement of diagnosis of aseptic loosening, there is still a great deal of uncertainty regarding its applicability in diagnostic algorithm. Therefore, in this meta-analysis, we aimed to investigate the diagnostic performance of SPECT/CT for identification of aseptic loosening in patients with persistent pain following the total knee arthroplasty (TKA) and total hip arthroplasty (THA). Electronic databases including Medline, Scopus, Web of Science, Cochrane library, and Embase were systematically searched for identifying relevant published studies from their inception to April 2023. Quality evaluation of the included studies was carried out using Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). SPECT/CT had pooled sensitivity of 94% (95% CI: 92-95%) and pooled specificity of 86% (95% CI: 83-89%) for diagnosis of aseptic loosening. The pooled positive likelihood ratio (LR) was estimated as 6.92 (95% CI: 3.74-12.81), the pooled negative LR was estimated as 0.1 (95% CI: 0.06-0.16), and the pooled diagnostic odds ratio (DOR) was estimated as 89.82 (95% CI: 33.04- 244.21). The Summary receiver operating characteristics (SROC) analysis revealed high accuracy with an area under curve (AUC) of 0.96. The findings of this meta-analysis revealed that SPECT/CT has high sensitivity and specificity for diagnosis of aseptic loosening in patients who underwent TKA or THA. Therefore, SPECT/CT can be considered as an encouraging diagnostic adjunct, particularly in cases with uncertain results of bone scan.

Is there an increased revision rate due to early tibial component loosening with a modern total knee arthroplasty design? A retrospective analysis from a large volume arthroplasty centre

BACKGROUND

The Attune TKR was introduced in 2011 as a successor to its predicate design The PFC Sigma. However, following reports of early failures, there are ongoing concerns related to increased loosening rates. Given the concerns, this study aimed to compare revision rates of the Attune implant to an established predicate, and other implant designs used in a high-volume arthroplasty center.

METHODS

We identified 10,202 patients who underwent primary cemented TKR at our institution with a minimum of 1 year follow-up, involving 2406 Attune TKR (557 S +), 4642 PFC TKR, 3154 other designs. Primary outcomes were revision for all-causes, aseptic loosening of any component, and aseptic tibial loosening. Kaplan-Meier survival and Cox regression models were used to compare groups. Matched cohorts were selected for radiographic analysis.

RESULTS

308 knees were revised. The Attune cohort had the lowest risk of revision, with a rate of 2.98 per 1000 implant-years while the PFC and All Other Implant groups had a rate of 3.15 and 4.4 respectively. Aseptic loosing was the most common cause for revision, with 76% (65/88) involving the tibia. Survival analysis showed no significant differences between the Attune and other cohorts. Radiolucent lines were detected in 7.1% of the Attune S + group, 6.8% of the standard Attune group, and 6.3% of the PFC group, with no significant differences found between them.

CONCLUSION

This study represents the largest non-registry review of the Attune TKR in comparison to a predicate and other designs. There was no significant increased revision rate for all-cause revision or aseptic loosening, or peri-implant radiolucencies. It appears that increased loosening may not be as concerning as originally thought.

LEVEL OF EVIDENCE

Level III.

In vivo evaluation of hyaluronic acid-polyethylene glycol amended PMMA bone cement for orthopaedic application

The utilization of polymethyl methacrylate (PMMA) bone cement is employed for the purpose of stabilizing fractured vertebral bodies. The existence of a mechanical imbalance in hard polymethylmethacrylate (PMMA) bone cement has the potential to increase the likelihood of a fracture occurring in the neighbouring vertebral body. In order to reduce potential difficulties, the primary goal of this study is to investigate the potential benefits of increasing PMMA bone cement's bioactivity and lowering its elastic modulus. The incorporation of a 10% volume fraction of hyaluronic acid (HyA) and polyethylene glycol (PEG) into the bone cement led to an improvement in the bioactivity and decreasing of elastic modulus of polymethylmethacrylate (PMMA). The integration of HyPE gel phase presents several advantages over pure PMMA bone cement, including enhanced setting parameters, improved degradability, and increased biocompatibility. The gel phase is additionally accountable for a reduction in the elastic modulus of polymethylmethacrylate (PMMA) bone cement. In addition, the existence of a porous structure that arises from the degradation of the HyPE gel phase delivers a significant amount of room, thereby enhancing the process of bone regeneration when implanted in the femur of rabbits. The utilization of HyPE in PMMA has been shown through comprehensive µ-CT analysis to enhance bone formation, thereby promoting osteointegration at the implantation site. Furthermore, the histological analysis demonstrated the existence of osteogenic activity in the PMMA polyethylene glycol supplemented with 10% HyA and 10% PEG after a 2-month period subsequent to implantation.

Passive Biotelemetric Detection of Tibial Debonding in Wireless Battery-Free Smart Knee Implants

Aseptic loosening is the dominant failure mechanism in contemporary knee replacement surgery, but diagnostic techniques are poorly sensitive to the early stages of loosening and poorly specific in delineating aseptic cases from infections. Smart implants have been proposed as a solution, but incorporating components for sensing, powering, processing, and communication increases device cost, size, and risk; hence, minimising onboard instrumentation is desirable. In this study, two wireless, battery-free smart implants were developed that used passive biotelemetry to measure fixation at the implant-cement interface of the tibial components. The sensing system comprised of a piezoelectric transducer and coil, with the transducer affixed to the superior surface of the tibial trays of both partial (PKR) and total knee replacement (TKR) systems. Fixation was measured via pulse-echo responses elicited via a three-coil inductive link. The instrumented systems could detect loss of fixation when the implants were partially debonded (+7.1% PKA, +32.6% TKA, both p < 0.001) and fully debonded in situ (+6.3% PKA, +32.5% TKA, both p < 0.001). Measurements were robust to variations in positioning of the external reader, soft tissue, and the femoral component. With low cost and small form factor, the smart implant concept could be adopted for clinical use, particularly for generating an understanding of uncertain aseptic loosening mechanisms.

Cementing Techniques In Knee Surgery (CeTIKS): a UK expert consensus study

Aims

Aseptic loosening is the most common cause of failure following cemented total knee arthroplasty (TKA), and has been linked to poor cementation technique. We aimed to develop a consensus on the optimal technique for component cementation in TKA.

Methods

A UK-based, three-round, online modified Delphi Expert Consensus Study was completed focusing on cementation technique in TKA. Experts were identified as having a minimum of five years' consultant experience in the NHS and fulfilling any one of the following criteria: a 'high volume' knee arthroplasty practice (> 150 TKAs per annum) as identified from the National joint Registry of England, Wales, Northern Ireland and the Isle of Man; a senior author of at least five peer reviewed articles related to TKA in the previous five years; a surgeon who is named trainer for a post-certificate of comletion of training fellowship in TKA.

Results

In total, 81 experts (round 1) and 80 experts (round 2 and 3) completed the Delphi Study. Four domains with a total of 24 statements were identified. 100% consensus was reached within the cement preparation, pressurization, and cement curing domains. 90% consensus was reached within the cement application domain. Consensus was not reached with only one statement regarding the handling of cement during initial application to the tibial and/or femoral bone surfaces.

Conclusion

The Cementing Techniques In Knee Surgery (CeTIKS) Delphi consensus study presents comprehensive recommendations on the optimal technique for component cementing in TKA. Expert opinion has a place in the hierarchy of evidence and, until better evidence is available these recommendations should be considered when cementing a TKA.

Novel Tuning of PMMA Orthopedic Bone Cement Using TBB Initiator: Effect of Bone Cement Extracts on Bioactivity of Osteoblasts and Osteoclasts

Bone cement containing benzoyl peroxide (BPO) as a polymerization initiator are commonly used to fix orthopedic metal implants. However, toxic complications caused by bone cement are a clinically significant problem. Poly (methyl methacrylate) tri-n-butylborane (PMMA-TBB), a newly developed material containing TBB as a polymerization initiator, was found to be more biocompatible than conventional PMMA-BPO bone cements due to reduced free radical generation during polymerization. However, free radicals might not be the only determinant of cytotoxicity. Here, we evaluated the response and functional phenotypes of cells exposed to extracts derived from different bone cements. Bone cement extracts were prepared from two commercial PMMA-BPO cements and an experimental PMMA-TBB. Rat bone marrow-derived osteoblasts and osteoclasts were cultured in a medium supplemented with bone cement extracts. More osteoblasts survived and attached to the culture dish with PMMA-TBB extract than in the culture with PMMA-BPO extracts. Osteoblast proliferation and differentiation were higher in the culture with PMMA-TBB extract. The number of TRAP-positive multinucleated cells was significantly lower in the culture with PMMA-TBB extract. There was no difference in osteoclast-related gene expression in response to different bone cement extracts. In conclusion, PMMA-TBB extract was less toxic to osteoblasts than PMMA-BPO extracts. Although extracts from the different cement types did not affect osteoclast function, PMMA-TBB extract seemed to reduce osteoclastogenesis, a possible further advantage of PMMA-TBB cement. These implied that the reduced radical generation during polymerization is not the only determinant for the improved biocompatibility of PMMA-TBB and that the post-polymerization chemical elution may also be important.